NEW DELHI — India has moved a step closer to integrate its nuclear submarines with ballistic missiles after the successful test launch of a medium-range missile from a submerged platform or pontoon in the Bay of Bengal.

The 10-meter tall, nuclear-capable missile was launched from a depth of about 50 meters on Jan. 27, says Defense Research and Development Organization Director General V.K. Saraswat.

“The missile was tested for its full range and met every mission objective,” Saraswat says. It rose to an altitude of 12 mi. and reached a distance of nearly 434 mi. before it fell into the Bay of Bengal.

All the parameters of the vehicle were monitored by radar throughout the trajectory and terminal events took place exactly as expected, Saraswat says.

The Submarine-Launched Ballistic Missile (SLBM), designated K-15, was successfully test launched more than a dozen times earlier, but in secret. “This is SLBM’s last trial of the development phase,” Saraswat says. “With the completion of developmental trials, the process of integrating SLBM with INS Arihant, the indigenously-built nuclear submarine, will commence soon,” he says.

According to other scientists, as many as 12 nuclear-capable missiles, each weighing 6 tons, will be integrated with Arihant, which will be powered by an 80-megawatt thermal reactor that employs uranium as fuel and light water as coolant and moderator. The reactor has been integrated with the submarine. Harbor trials are expected to begin in June.

With this test, India has joined an elite group of nations capable of lofting nuclear missiles from air, land and sea, the scientists says.

A.K. Chakrabarty, chief scientist who designed the SLBM and director of the Hyderabad-based Defense Research and Development Laboratory, says the next big challenge will be to test the missile when it is fitted on Arihant in the next few months.

“Development of [the] missile system is an ongoing process. So many other tests are to be done yet,” Chakrabarty says. “It is going on in normal course and the continuous success will lead to an early deployment of the weapons system.”

Defense Minister A.K. Antony told India’s parliament last May that Arihant might enter service in the first half of 2013.

This capability would complete India’s nuclear triad, making the country capable of launching missiles from air, land and sea. The triad’s other elements are the Agni missile with a range up to 3,106 mi., and the Mirage-2000, Su-30MKI and MiG-29 fighters.

Indian defense scientists are developing another SLBM (K-5) with a range of nearly 1,864 mi.